The present invention relates to a recording medium such as an optical recording medium used particularly as write-once recording media as well as relates to a recording apparatus, a recording method, a reproduction apparatus and a reproduction method, which are provided for the recording medium.
As a technology for recording and reproducing digital data, there is known a data-recording technology for using optical disks including magneto-optical disks as recording media. Examples of the optical disks are a CD (Compact Disk), an MD (Mini-Disk) and a DVD (Digital Versatile Disk). The optical disk is the generic name of recording media, which is a metallic thin plate protected by plastic. When a laser beam is radiated to the optical disk, the optical disk emits a reflected signal, from which changes can be read out as changes representing information recorded on the optical disk.
The optical disks can be classified into a read-only category including a CD, a CD-ROM and a DVD-ROM, which the user is already familiar with, and a writable category allowing data to be written therein as is generally known. The writable category includes an MD, a CD-R, a CD-RW, a DVD-R, a DVD-RW, a DVD+RW and a DVD-RAM. By adopting a magneto-optical recording method, a phase-change recording-method or a pigmented-coat change recording-method for the writable category, data can be recorded onto a disk of this category. The pigmented-coat change recording-method is also referred to as a write-once recording-method. Since this pigmented-coat change recording-method allows data recording once and inhibits renewal of data onto the optical disk, the optical disk is good for data-saving applications or the like. On the other hand, the magneto-optical recording method and the phase-change recording-method are adopted in a variety of applications allowing renewal of data. The applications allowing renewal of data include mainly an application of recording various kinds of content data including musical data, movies, games and application programs.
In addition, in recent years, a high-density optical disk called a blue-ray disc has been developed in an effort to produce the product on a very large scale.
Typically, data is recorded onto a high-density optical disk and read out from the optical disk under a condition requiring a combination of a laser with a wavelength of 405 nm and an objective lens with an NA of 0.85 to be reproduced. The laser required in this condition is the so-called blue laser. With the optical disk having a track pitch of 0.32 μm, a line density of 0.12 μm/bit, a formatting efficiency of about 82% and a diameter of 12 cm, data of the amount of up to 23.3 GB (gigabytes) can be recorded onto and reproduced from the optical disk in recording/reproduction units, which are each a data block of 64 KB (kilobytes).
There are also two types of optical disk having such a high density, i.e., optical disks of a write-once type and optical disks of a rewritable type.
In addition, in the case of recording media usable as media for recording these kinds of data or not as reproduction-only media, there is known a technology for changing a data-recording location on the optical disk by providing an alternate area. That is to say, this technology is a defect management technology whereby an alternate recording-area is provided so that, if a location improper for recording data exists on the optical disk due to a defective damage on the optical disk, the alternate recording-area can be used as an area serving as a substitute for the defective location to allow proper recording and reproduction operations to be carried out.
For example, the defect management technology is disclosed in U.S. Pat. No. 6,782,488 (hereinafter referred to as Patent Document 1).
By the way, it is naturally impossible to record data into an already recorded area in a write-once optical recording medium, that is, an area in which data has been recorded before. Examples of the write-once optical recording medium are a CD-R, a DVD-R and a high-density recording medium, which function as a write-once disk.
Specifications of most file systems to be recorded on an optical recording medium are defined by assuming the use of the optical recording medium as a ROM-type disk or a RAM-type disk. The ROM-type disk is a reproduction-only medium and the RAM-type disk is a rewritable optical disk. Specifications of a file system for a write-once recording medium allowing data to be stored therein only once limit functions of the ordinary file system and include special functions.
The specifications of a file system for a write-once recording medium are a reason why the file system does not become widely popular. On the other hand, a FAT file system capable of keeping up with a variety of OSes of an information-processing apparatus and other file systems cannot be applied to write-once media as they are.
Write-once media is widely used typically in applications of preserving data. If the write-once media can also be used for the FAT file system by keeping the general specifications of the file system as they are, the usability of the write-once media can be further enhanced.
In order to allow a widely used file system such as the FAT file system and a file system for RAMs or hard disks to be applied to write-once media as it is, however, a function to write data into the same address as that of existing data is required. That is to say, a capability of renewing data is required. Of course, one of characteristics of the write-once media is that data cannot be rewritten onto the media for the second time. Thus, it is impossible to use a file system for such a rewritable recording medium as it is in the first place.
In order to compensate for the above shortcomings, as disclosed in the Patent Document 1 described above, in the case of write-once media such as an optical disk with an alternate area existing thereon, there have been proposed technologies for implementing a data overwrite function using alternate-address information and the alternate area.
By introducing such technologies, a file system provided for RAMs and ROMs can be used without the need to limit and add functions and, from the application point of view, it is no longer necessary to be aware of differences in recording technique among different kinds of media.
However, these technologies allowing data on write-once media to be renewed absolutely require that an alternate area be set on each of disks. In addition, the proper sizes of the alternate areas cannot be set at a uniform value if it is necessary to consider, among others, the compatibility of the application with the media as well as the compatibility of the apparatus with the media.
For the reasons described above, it is necessary to allocate as many alternate areas as possible or more alternate areas than actually required from the beginning at a formatting time, and a large number of alternate areas has an effect on a method of utilizing user-data areas with a high degree of efficiency.